You don't have to. However if you support them they get enough money to make it worthwhile to do more. Some of the bigger ones make enough money that producing videos you like is their day job, if you don't pay them (ads count) then they will have to find a new job.
Only some. One of my favorite channels isn't sponsored at all, and is ad free.
> the content creators are losing out by your adblockers, not youtube
Why do I have to financially support content creators without question? Please explain this to me.